Some of it is holdover from various economic depressions that are holding on tight to our collective habits.
My wife and I both favor bulk shopping for a majority of our household goods, and when we pondered why, it came down to our families having done the same and followed that thread to our grand/great-grand parents that lived through the great depression.
Having bulk food/household goods means that at any point, if income halts for any reason, we still have X number of meals/tp rolls/litter changes before we enter the danger zone. That was reassuring when we were living paycheck to paycheck.
I do agree on urban planning being a part of it as well. It's a 15min drive to my closest grocery store, and 10 minutes of that is driving out of my neighborhood. Walking to the store is nearly impractical, and generally not safe due to the lack of sidewalks for a fair stretch of the main road.